There are many advantages to advancing articles in a single file manner along a path for treatment. For example, articles are readily fed into and removed from such a file and article speed is readily controlled. Also, all articles in a close ordered file are readily started and stopped and each article is easily sensed or otherwise inspected. A problem is to apply an escapement to such a file so individual articles may be set apart for treatment. Another problem is to apply such an escapement to small, lightweight articles which are often difficult to handle.
Such small articles may include light emitting diodes (LEDs) which often have a tiny optical head and a pair of wire leads depending therefrom disposed along a plane. Portions of such articles are often treated in a successive manner. For example, the leads of such an LED may be trimmed at a first station and then shaped into a precise, offset configuration at a second station. It is advantageous to advance the LEDs in a single file for such treatment because of guiding and orientation problems. Therefore, it is desirable to apply an escapement to the file to feed individual articles and position the same at successive stations for treatment.
Single file escapements are provided in several forms in industries concerned with packaging materials in bottles. For example, in filling beverage bottles a single file thereof is advanced along a path by a conveyor belt. A typical escapement employs resilient fingers which are thrust across the belt in timed cycles to accurately space empty bottles on the moving belt. Thereafter, overhead means are moved in synchronism with the spaced bottles to perform work thereon. Another type of escapement controls a file of bottles at a filling station where successive leading bottles are stopped, filled and released and successive trailing bottles are indexed for the same treatment. Neither type of escapement feeds articles to successive stations along a path and positions the same for successive, but different treatments. Instead successive treatments are made by moving means parallel to and in time with spaced articles, or separate files of articles are created and each is stopped so leading articles may be treated.
Another advantage to advancing articles in a single file manner along a path is that a track structure may be utilized to guide and maintain orientation of the articles. Motive power may be provided by gravity, by mechanical means or often more conveniently, by fluid power. For example, articles such as silicon wafers in the electronics industry, are readily advanced in an easily observed, open track on a cushion of air. However, such a fluid powered track is not normally suitable for articles such as LEDs because they are generally devoid of major flat surfaces. Also, when escapements are utilized having fingers extending transversely of such a track, fluid flow is at least partially obstructed. Nevertheless, fluid powered tracks have desirable advantages such as simplicity, low cost and speed which make it attractive to use fluid power to advance articles such as LEDs for treatment.
Accordingly, it is desirable to develop new and improved expedients for feeding articles to successive stations for treatment. It is further desirable to feed the articles in a single file manner along a path to the stations. Individual articles should be singled out from a waiting file in the path and serially positioned at each successive station located along the same path. Such articles should be securely positioned and then securely repositioned for successive mechanical treatments at the successive stations.
It is also desirable to utilize a track structure to guidably advance the articles to the successive stations for treatment. Such track should guidably advance even small, lightweight articles which may be devoid of major, flat surfaces. Preferably the track should be fluid powered in such a manner that escapement fingers may be tolerated in the path without seriously impeding advancement of the articles.